Functionally deficient bridges are defined as those that do not have the lane
widths, shoulder widths, or vertical clearances adequate to serve traffic demand,
or the bridge may not be able to handle occasional roadway flooding.

Data for 1990, 1992, 1997-99, and 2001 are as of December of those years; data
for 1991 and 1994-96 are as of June of those years; data for 1993 are as of
September of that year; data for 2000 are as of August of that year.